The surface wetting of five biopolymers, used as coating materials for a plastic film, was monitored over a span of 8 min by means of the optical contact angle technique. Because most of the total variation was observed to occur during the first 60 s, we decided to focus on this curtailed temporal window. Initial contact angle values ranged from 91 for chitosan to 30 degrees for pullulan. However, the water drop profile began to change immediately following drop deposition for all biocoatings, confirming that the concept of water contact angle equilibrium is not applicable to most biopolymers. First, a threeparameter decay equation [¦È(t) = ¦È(0) exp(ktn)] was fit to the experimental contact angle data to describe the kinetics of the contact angle change for each biocoating. Interestingly, the k constant correlated well with the contact angle evolution rate and the n exponent seemed to be somehow linked to the physicochemical phenomena underlying the overall kinetics process. Second, to achieve a reliable description of droplet evolution, the contact angle (CA) analysis was coupled with image analysis (IA) through a combined geometric/trigonometric approach. Absorption and spreading were the key factors governing the overall mechanismof surface wetting during the 60 s analysis, although the individual quantification of both phenomena demonstrated that spreading provided the largest contribution for all biopolymers, with the only exception of gelatin, which showed two quasi-equivalent and counterbalancing effects. The possible correlation between these two phenomena and the topography of the biopolymer surfaces are then discussed on the basis of atomic force microscopy analyses.

Wetting of Biopolymer Coatings: Contact Angle Kinetics and Image Analysis Investigation / S. Farris, L. Introzzi, P. Biagioni, T. Holz, A. Schiraldi, L. Piergiovanni. - In: LANGMUIR. - ISSN 0743-7463. - 27:12(2011 May 27), pp. 7563-7574. [10.1021/la2017006]

Wetting of Biopolymer Coatings: Contact Angle Kinetics and Image Analysis Investigation

S. Farris
Primo
;
L. Introzzi
Secondo
;
A. Schiraldi
Penultimo
;
L. Piergiovanni
Ultimo
2011

Abstract

The surface wetting of five biopolymers, used as coating materials for a plastic film, was monitored over a span of 8 min by means of the optical contact angle technique. Because most of the total variation was observed to occur during the first 60 s, we decided to focus on this curtailed temporal window. Initial contact angle values ranged from 91 for chitosan to 30 degrees for pullulan. However, the water drop profile began to change immediately following drop deposition for all biocoatings, confirming that the concept of water contact angle equilibrium is not applicable to most biopolymers. First, a threeparameter decay equation [¦È(t) = ¦È(0) exp(ktn)] was fit to the experimental contact angle data to describe the kinetics of the contact angle change for each biocoating. Interestingly, the k constant correlated well with the contact angle evolution rate and the n exponent seemed to be somehow linked to the physicochemical phenomena underlying the overall kinetics process. Second, to achieve a reliable description of droplet evolution, the contact angle (CA) analysis was coupled with image analysis (IA) through a combined geometric/trigonometric approach. Absorption and spreading were the key factors governing the overall mechanismof surface wetting during the 60 s analysis, although the individual quantification of both phenomena demonstrated that spreading provided the largest contribution for all biopolymers, with the only exception of gelatin, which showed two quasi-equivalent and counterbalancing effects. The possible correlation between these two phenomena and the topography of the biopolymer surfaces are then discussed on the basis of atomic force microscopy analyses.
contact angle; biopolymers; wetting
Settore AGR/15 - Scienze e Tecnologie Alimentari
Settore CHIM/02 - Chimica Fisica
27-mag-2011
pubs.acs.org/Langmuir
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/167214
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